1. Field of the Invention
The present invention relates to a wavelength selective switch.
2. Related Background Art
A wavelength selective switch is disclosed in U.S. Pat. No. 7,397,980 and Japanese Patent Application Laid-Open No. 2011-248000. The wavelength selective switch includes a plurality of port groups that include input ports and output ports. A beam input from the input port of each port group is deflected independently in an individual deflection area.
A wavelength selective switch in which an optical axis of a beam input from a certain port group and an optical axis of a beam input from other port group are inclined in directions opposite to each other for a predetermined axis is known. For example, when an optical element included in an optical system has a refractive index boundary surface vertical to the predetermined axis, the beam input from the input port of the certain port group may return to an input port of a different port group.